• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.400-405
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• 2018

This paper presents a compact ultra-wideband (UWB) flexible monopole antenna design on a paper substrate. The proposed antenna is made of iterations of a circular slot inside an octagonal metallic patch. This fractal-based geometry has been deployed to achieve compactness along with improved bandwidth, measured reflection coefficient -10 dB bandwidth ranging from 2.7 to 15.8 GHz. The overall size of the antenna is $26mm{\times}19mm{\times}0.5mm$, which makes it a compact one. The substrate used is paper and the main features like environment friendly, flexibility, green electronics applications and low cost of fabrication are the key factors for the proposed antenna. The aforementioned UWB prototype is suitable for many wireless communication systems such as WiMAX, WiFi, RFID and WSN applications. Antenna has been tested for the effect of bending by placing it over a curved surface of a very small radius of 10 mm.

• Wind and Structures
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• v.28 no.5
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• pp.271-284
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• 2019

This paper describes the application of a novel virtual prototyping methodology to wind turbine blade design. Numeric modelling data and experimental data about turbine blade geometry and structural/dynamical behaviour are combined to obtain an affordable digital twin model useful in reducing the undesirable uncertainties during the entire turbine lifecycle. Moreover, this model can be used to track and predict blade structural changes, due for example to structural damage, and to assess its remaining life. A new interactive and recursive process is proposed. It includes CAD geometry generation and finite element analyses, combined with experimental data gathered from the structural testing of a new generation wind turbine blade. The goal of the research is to show how the unique features of a complex wind turbine blade are considered in the virtual model updating process, fully exploiting the computational capabilities available to the designer in modern engineering. A composite Sandia National Laboratories Blade System Design Study (BSDS) turbine blade is used to exemplify the proposed process. Static, modal and fatigue experimental testing are conducted at Clarkson University Blade Test Facility. A digital model was created and updated to conform to all the information available from experimental testing. When an updated virtual digital model is available the performance of the blade during operation can be assessed with higher confidence.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.12
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• pp.4866-4888
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• 2020

One major and time-consuming task in fish production is obtaining an accurate estimate of the number of fish produced. In most Nigerian farms, fish counting is performed manually. Digital image processing (DIP) is an inexpensive solution, but its accuracy is affected by noise, overlapping fish, and interfering objects. This study developed a catfish recognition and counting algorithm that introduces detection before counting and consists of six steps: image acquisition, pre-processing, segmentation, feature extraction, recognition, and counting. Images were acquired and pre-processed. The segmentation was performed by applying three methods: image binarization using Otsu thresholding, morphological operations using fill hole, dilation, and opening operations, and boundary segmentation using edge detection. The boundary features were extracted using a chain code algorithm and Fourier descriptors (CH-FD), which were used to train an artificial neural network (ANN) to perform the recognition. The new counting approach, based on the geometry of the fish, was applied to determine the number of fish and was found to be suitable for counting fish of any size and handling overlap. The accuracies of the segmentation algorithm, boundary pixel and Fourier descriptors (BD-FD), and the proposed CH-FD method were 90.34%, 96.6%, and 100% respectively. The proposed counting algorithm demonstrated 100% accuracy.

• East Asian mathematical journal
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• v.30 no.2
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• pp.173-195
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• 2014

This study, utilizing several features about plane figures covered in the current secondary curriculum of mathematics and reviewing two solutions to cube duplication problem presented by Menaechmus, proving the solution by Nicomedes and visualizing solutions based on Apollonius' 'Conics' by medieval Islam geometricians such as Ab$\bar{u}$ Bakr al-Haraw$\bar{i}$, AbAb$\bar{u}$ J$\acute{a}$far al-Kh$\bar{a}$zin, Nas$\bar{i}$r al-D$\bar{i}$n al-T$\bar{u}s\bar{i}$, Y$\bar{u}$suf al-Mu'taman ibn H$\bar{u}$d, introduce to teachers and students in the field where the question of cube duplication problem comes from and which solving method has developed it and suggests new methods for visualization using dynamic geometry program as well so that the contents reviewed can be used in the filed. The solving methods to cube duplication problem in this paper are very creative and increase the practicality, efficiency and value of Mathematics, and provide students and teachers with the opportunities to reconfirm the importance and beauty of basic knowledge in the secondary geometry in the process of visualization of drawing figures using dynamic geometry program.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.35-41
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• 2004

In computational study on RF(Radio Frequency) plasmas, a 1D fluid models with an advantage of a short computational time are often adopted. However, in order to obtain realistic calculation results under a typical chamber geometry with unequal-sized electrodes, modeling of the plasma space is an issue to be investigated. In this paper, it is focused on that how much a 1D model can approximate a 2D model. 1D fluid models with unequal-sized electrodes, which have spherical and frustum geometry systems, were developed and their results were compared with those of 2D model with Gaseous Electronic Conference cell structure. Behavior of $N_2$ RF plasmas has been simulated using 1D and 2D fluid models and a technique to take account of unequal-sized electrodes in a 1D fluid models has been examined. Features of the plasma density and the electric potential were discussed as characteristic quantities representing the asymmetry of the chamber geometry.

• Journal of the Korean School Mathematics Society
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• v.21 no.2
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• pp.113-139
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• 2018

There is no doubt about the importance of teacher knowledge for good teaching. Many researches attempted to conceptualize elements and features of teacher knowledge for teaching in a quantitative way. Unlike existing researches, this article suggests an interpretation of preservice teacher knowledge in the field of geometry using the Shulman - Fischbein framework in a qualitative way. Seven female preservice teachers voluntarily participated in this research and they performed a series of written tasks that asked their subject matter knowledge (SMK) and pedagogical content knowledge (PCK). Their responses were analyzed according to mathematical algorithmic -, formal -, and intuitive - SMK and PCK. The interpretation revealed that preservice teachers had overally strong SMK, their deeply rooted SMK did not change, their SMK affected their PCK, they had appropriate PCK with regard to knowledge of student, and they tended to less focus on mathematical intuitive - PCK when they considered instructional strategies. The understanding of preservice teachers' knowledge throughout the analysis using Shulman-Fischbein framework will be able to help design teacher preparation programs.

• Economic and Environmental Geology
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• v.26 no.2
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• pp.227-237
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• 1993

Lineaments in the Kyungsang basin most intensely develop in the East coast domain including the Yangsan fault, which dominantly run in NNE direction. The geometry of small fault population near or along the Yangsan fault represents the dominant strikes of N35E, high angle dips and shallowly plunging rakes with dextral movement sense. Stereographic solution on the Yangsan fault geometry gives the dip of 88SE, the slip direction of 17,024 and the slip rake of 18, which were determined from the strike (N23E) of the fault measured on map, and the average attitude (N35E, 84SE) and fault striation (16, 037) of small fault population considered as Riedel shears. It is judged from the geometry of small fault population to the main Yangsan fault and dragging features of bedding attitude near the fault that the Yangsan fault was produced from dextrally strike-slip movement. The movement of the Yangsan and the adjacent parallel faults is thought to be taken place much later than the other fault sets in the Kyungsang basin. It might occur during the geologic age from Eocence to early Miocene according to the consideration of K-Ar ages of the igneous rocks near the fault. The estimated paleostress state indicates ENE shortening and NNW extension. The displacement of the Yangsan fault in the study area is not constant along the fault but decreases from the south to the north. Taking the northern end of the study area as a separating point the whole extension of the Yangsan fault may be divided into southern and northern segments.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.577-582
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• 2007

A variational formulation for plane elasticity problems is derived based on an isogeometric approach. The isogeometric analysis is an emerging methodology such that the basis functions in analysis domain arc generated directly from NURBS (Non-Uniform Rational B-Splines) geometry. Thus. the solution space can be represented in terms of the same functions to represent the geometry. The coefficients of basis functions or the control variables play the role of degrees-of-freedom. Furthermore, due to h-. p-, and k-refinement schemes, the high order geometric features can be described exactly and easily without tedious re-meshing process. The isogeometric sensitivity analysis method enables us to analyze arbitrarily shaped structures without re-meshing. Also, it provides a precise construction method of finite element model to exactly represent geometry using B-spline base functions in CAD geometric modeling. To obtain precise shape sensitivity, the normal and curvature of boundary should be taken into account in the shape sensitivity expressions. However, in conventional finite element methods, the normal information is inaccurate and the curvature is generally missing due to the use of linear interpolation functions. A continuum-based adjoint sensitivity analysis method using the isogeometric approach is derived for the plane elasticity problems. The conventional shape optimization using the finite element method has some difficulties in the parameterization of boundary. In isogeometric analysis, however, the geometric properties arc already embedded in the B-spline shape functions and control points. The perturbation of control points in isogeometric analysis automatically results in shape changes. Using the conventional finite clement method, the inter-element continuity of the design space is not guaranteed so that the normal vector and curvature arc not accurate enough. On tile other hand, in isogeometric analysis, these values arc continuous over the whole design space so that accurate shape sensitivity can be obtained. Through numerical examples, the developed isogeometric sensitivity analysis method is verified to show excellent agreement with finite difference sensitivity.

• Journal of Computational Design and Engineering
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• v.3 no.2
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• pp.161-177
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• 2016

In history based parametric CAD modeling systems, persistent identification of the topological entities after design modification is mandatory to keep the design intent by recording model creation history and modification history. Persistent identification of geometric and topological entities is necessary in the product design phase as well as in the re-evaluation stage. For the identification, entities should be named first according to the methodology which will be applicable for all the entities unconditionally. After successive feature operations on a part body, topology based persistent identification mechanism generates ambiguity problem that usually stems from topology splitting and topology merging. Solving the ambiguity problem needs a complex method which is a combination of topology and geometry. Topology is used to assign the basic name to the entities. And geometry is used for the ambiguity solving between the entities. In the macro parametrics approach of iCAD lab of KAIST a topology based persistent identification mechanism is applied which will solve the ambiguity problem arising from topology splitting and also in case of topology merging. Here, a method is proposed where no geometry comparison is necessary for topology merging. The present research is focused on the enhancement of the persistent identification schema for the support of ambiguity problem especially of topology splitting problem and topology merging problem. It also focused on basic naming of pattern features.

• Polymer(Korea)
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• v.35 no.6
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• pp.505-512
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• 2011

Effects of structural features of 4 dinuclear constrained geometry catalysts having paraxylene derivative bridge (DCGC) on copolymerization of ethylene and 1-hexene were investigated. The bridges of three catalysts have para-xylene backbone with a different substituent at benzene ring. The substituents were hydrogen (Catalyst 1), isopropyl (Catalyst 2), n-hexyl (Catalyst 3) and 1-octyl (Catalyst 4). It was found that Catalyst 1 having hydrogen as a substituent exhibited the greatest activity among the four dinuclear CGCs. On the other hand, Catalyst 2 containing isopropyl as a substituent showed the smallest activity. Very interestingly, Catalyst 2 was able to produce about 6 times higher molecular weight polymer than Catalyst 3 and 4. Catalyst 3 and 4 having a long alkyl chain substituent revealed the biggest comonomer response to generate polyethylene copolymer containing more than 40% 1-hexene contents. These results suggest that the control of the substituent of para-xylene bridge of dinuclear CGC can provide a proper method to adjust the microstructure of polyethylene copolymers.